Silicone rubbers have excellent electrical characteristics and as a result are frequently used for high-voltage insulators and articles such as anode caps, plug boots, insulators, flame-retardant wire and cable, and the like. The silicone rubber compositions used for these applications have typically contained large amounts of inorganic filler, e.g., aluminum hydroxide powder, aluminum oxide powder, or quartz powder. See, for example, Japanese Patent Publication 53-35982, Japanese Patent Publication 62-26124, and Japanese Patent Application Laid Open Number 4-209655.
However, liquid silicone rubber compositions that are highly loaded with these inorganic fillers have very high viscosities. This gives these compositions poor moldability, and makes them difficult to use in applications that require the fluidities appropriate for injection molding or casting materials. In addition, the silicone rubber moldings afforded by the cure of highly filled silicone rubber compositions have low mechanical strengths. Under conditions of exposure to severe soiling or the weather, these compositions will also suffer from such deterioration phenomena as tracking and erosion due to the high electrical stresses, which results in a drastic decline in their high-voltage insulating properties and has prevented these compositions from being completely acceptable.
Therefore, there is a need for a liquid silicone rubber composition that prior to its cure has a desirable fluidity and excellent moldability, and that can be cured to give very mechanically strong silicone rubber moldings that have excellent high-voltage insulating properties.